Chapter 4 Literals, Variables, and Constants

4.3.1 Variable’s Initial Value – Initialization

• Initialization
• Process of giving a variable a value during its declaration
• Results in the variable always being in a known state
• When declared, a variable’s initial value is unknown
• Important to provide an initial value for all variables

int sum = 0;

int Calvins_age = RETIREMENT_AGE;

int base_salary = 30000;

int num_dependents, staff_salary = base_salary;

4.3.1 Variable’s Initial Value – Alternate Forms

int sum ( 0 );

int Calvins_age( RETIREMENT_AGE);

• Fully uniform type initialization
• Introduced in C++11

int base_salary { 30000 };

int num_dependents, staff_salary { base_salary };

4.3.1 Variable’s Initial Value – Good Practices

• Always know the state, or value, of all variables
• Variables should always be initialized
• Variables, even characters, are usually initialized to 0

4.3.2 Data Types – Definition

• Data type
• Specifies how much memory a variable will take up in memory
• Indicates operations that can be performed on the variable
• Primitive data type
• Data type whose definition is built into the language

4.3.2 Data Types – Selected Types

C++ Data Type	Description of Data	Memory Allocated	Range
char	Character	1 byte	-128 to 127
int	Integer	4 bytes	–2,147,483,648 to 2,147,483,647
float	Floating point (decimal)	4 bytes	+/-3.4 x 1038 with 7 digits of accuracy
double	Double precision floating point	8 bytes	+/-1.7 x 10308 with 15 digits of accuracy
bool	Boolean data	1 byte	true or false
short (or short int)	Smaller integer	2 bytes	–32,768 to 32,767
long long (C++11)	Largest integer	8 bytes	+/-9.22 x 1018